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Antenna mods
- Thread starter djhoodrich
- Start date
Oh man, where to begin...
There's a thing called VSWR that is a measure of match to an antenna.
There's not an antenna on the planet that is out of the box a perfect match to your transmitter and receiver.
Add a signal booster onto that...
It isn't clear that the "amplifier" is receive only or transmit and receive. It's likely that it is only receive which means it can give you a false sense of range.
In either case another item in the pipeline to adjust for match.
Are there adjustments and instructions for how to line match these things?
If not you could actually be reducing your signal.
There's a thing called VSWR that is a measure of match to an antenna.
There's not an antenna on the planet that is out of the box a perfect match to your transmitter and receiver.
Add a signal booster onto that...
It isn't clear that the "amplifier" is receive only or transmit and receive. It's likely that it is only receive which means it can give you a false sense of range.
In either case another item in the pipeline to adjust for match.
Are there adjustments and instructions for how to line match these things?
If not you could actually be reducing your signal.
The way they sell this stuff is misleading - the actual max power delivered to the antenna is then multiplied by the supposed antenna gain to get a "effective" power. 3db is roughly twice the power so 5 db will jack that 1 watt real power "up" to 4watts claimed power. Thanks to the inverse square law into an omni antenna you get pretty insignificant gains in range.
I'm not exactly sure how two boosters on each side will work but if it is indeed 4 watts each then you'd be in violation of FCC regs - and trust me they will come looking if they get reports of interference.
Now those antennas appear to be a form of dipole with passive radiator/director. That's cool except that due to these being microwaves there's also interaction between the two antennas and in fact you could be getting phase cancellation. You could measure the distances to be sure - optimum isolation would come at 1/2 wavelengths - roughly 62 mm apart. That said I can only assume that DJI has already factored that into the inter antenna distance since the original antenna is a pair of simple monopoles.
To work properly as a director, the front passive element in each antenna (the "V"s) would need to be about 3mm apart. I can't tell from the photo but it looks like it may be close.
The gist of this is *if* the antennas are designed properly you might get a modest increase in signal simply from the fact they are being made slightly directional. The fact that they are dipoles will also make them much more sensitive to orientation - if you turn them at angle the signal will be reduced substantially.
Here's how the FCC sees it.
Maximum Transmit Output Power in the ISM bands
Several of the FCC part 15 rules govern the transmit power permited in the ISM bands. Here is a summary of those rules:
- Maximum transmitter output power, fed into the antenna, is 30 dBm (1 watt).
- Maximum Effective Isotropic Radiated Power (EIRP) is 36 dBm (4 watt).
The amp is for both transmit and receive. The amps help significantly with the proper antenna. It did help with those fpvlr yagi antenna, but there is a lot of interference resulting in poor video quality at times. I've had much better luck with the circular polarized antenna. I have RexUAV antenna which was intended for 3dr solo. It has amazing signal with the amps. I went out 54,200ft and total trip of of over 108,600ft in silicon valley and not once did I get low signal and video feed was perfect.
I don't have swr meter and not buying one. I wish I did. I've simply tested a number of products and selected the one that works best so far. At this point I'm battery limited. I have signal for 70,000ft plus, but need more battery to do it.
So with the RexUAV antenna you were able to travel 54,200ft one way? and round trip 108,600ft with a single battery?
With extra batteries attached, yes. Just under 40 minutes flight time.
RexUAV circular polarized with 2 sunhams boosters. The FPVLR version is just as good if not better. Here is a link to FPVLR one:
https://fpvlr.com/store/product/solo-v-2-long-range-kit-10-5dbi/
I would go with that one if I did it again. The RexUAV is a clone of that one.
They fly the mavic 499 meters high? That's like 1500 feet high, where is this? In China?
Guys, what is the actual difference between all of these antennas:
- circular polarized
- directional italite nano sync
- multidirectional
Plus what aux battery for mod you suggest?
Thanks so much lads
I
- circular polarized
- directional italite nano sync
- multidirectional
Plus what aux battery for mod you suggest?
Thanks so much lads
I
Yes, this was in China, i think they are testing the limits of this mod.
What I use it for is that, I live in HK, city full of skyscrapers, I mod this so it won't be to much of an interference. I didn't mod for pure breaking the limit
Looks like they have a CP kit now for Mavic MAVIC PRO CP ANTENNA KIT - FPVLR
anyone tried this? It looks more portable than the SOLO kit
anyone tried this? It looks more portable than the SOLO kit
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